The researchers started by growing the germanium/silicon nanowires on a cylindrical drum, which was then rolled onto a sticky substrate. The substrate used was a polyimide film, but the researchers said the technique can work with a variety of materials, including other plastics, paper or glass. As the drum rolled, the nanowires were deposited, or "printed," onto the substrate in an orderly fashion, forming the basis from which thin, flexible sheets of electronic materials could be built.